如何在JavaCanvas中绘制JSON文字？

Question

如何在 Android Canvas 中编写具有漂亮格式的 JSON object/string？

例如，

val jsonText = "{"profile":{"name": "Robert","account_id": "31"}}"

将被绘制成 Canvas 看起来像，

Answer 1

Canvas functions have some limitations as it draws all text in single line. If the width of the text exceeds the width of the Canvas, the text will be clipped. hence we use staticLayout for the same to show text in paragraph or multi-line approach.

下面的代码用于在 canvas 中显示 json 格式的文本，其中 json 从资产文件加载。

fun drawTextOnCanvas(activity: FragmentActivity) {
var canvas = Canvas(bitmap)
var textPaint=TextPaint()
textPaint.density=20f
textPaint.bgColor=Color.BLACK

val jsonText = activity.loadJSONFromAsset("demo.json")
val jsonObject = JSONObject(jsonText);
val text=jsonObject.toString(1)
val staticLayout=StaticLayout.Builder.obtain(text,0,text.length,textPaint,150)

staticLayout.build().draw(canvas)}

希望对您有所帮助！

Answer 2

生成 PDF

import android.graphics.Color
import android.graphics.Paint
import android.graphics.pdf.PdfDocument
import com.google.gson.GsonBuilder    

class PdfGeneratorService(){

    private val ROW_INC = 20F
    private val COL_INC = 15F
    
    fun jsonFormat(jsonStr: String): String {

        var indentCount = 0

        val builder = StringBuilder()
        for (c in jsonStr) {
            if (indentCount > 0 && '\n' == builder.last()) {
                for (x in 0..indentCount) builder.append("    ")
            }
            when (c) {
                '{', '[' -> {
                    builder.append(c).append("\n")
                    indentCount++
                }
                ',' -> builder.append(c).append("\n")
                '}', ']' -> {
                    builder.append("\n")
                    indentCount--
                    for (x in 0..indentCount) builder.append("    ")
                    builder.append(c)
                }
                else -> builder.append(c)
            }
        }

        return builder.toString()
    }

    private fun createPdf(textToPdf: String) {
        try {
            val gSon = GsonBuilder().setPrettyPrinting().create()
            val text = gSon.toJson(jsonFormat(textToPdf))

            val rawLines = text.split("\n")
            val jsonLines = rawLines.map { it.replace("\", "") }
            val maxLengthString = jsonLines.maxBy { it.length }

            val paint = Paint()
            paint.color = Color.BLACK
            paint.fontSpacing

            val pageWidth = paint.measureText(maxLengthString).toInt() + 2 * COL_INC.toInt() // 2, two side padding
            val pageHeight = (ROW_INC * rawLines.size + ROW_INC).toInt()

            val document = PdfDocument()
            val pageInfo: PdfDocument.PageInfo = PdfDocument.PageInfo.Builder(pageWidth, pageHeight, 1).create()
            val page: PdfDocument.Page = document.startPage(pageInfo)
            val canvas = page.canvas

            for (line in jsonLines) {
                canvas.drawText(line, column, row, paint)
                row += ROW_INC
            }

            document.finishPage(page)
            document.writeTo(FileOutputStream(File(PATH_TO_PDF_FILE)))
            document.close()
        }catch (e: java.lang.Exception){
            Log.e("classTag", e)
        }
    }
}

您可以找到有关如何使用的文章Gson

如何在JavaCanvas中绘制JSON文字？

How to draw JSON text in Java Canvas?

java

android

json

android-canvas

pretty-print

生成 PDF